1. Field of the Invention
The present invention relates to a low temperature rise type rolling bearing for use in such applications as speedup gears in a wind power generator. The present invention also relates to a bearing apparatus hard to supply grease periodically, such as a bearing apparatus incorporated into a main motor or the like to support the armature shaft of the main motor rotatably.
2. Description of the Related Art
During operation, a rolling bearing inevitably generates heat. Such generation of heat is attributed to {circle around (1)} agitation heat produced by the rolling elements and the cage agitating the lubricant, {circle around (2)} frictional heat caused by slides among components, such as those between the cage and the rolling elements and between the cage and the races, {circle around (3)} frictional heat produced by rolling friction between the rolling elements and the races, and the like.
The generation of heat may cause a significant rise in the temperature of the rolling bearing to pose problems including a larger amount of lubricating oil necessary to cool the bearing, a greater, more complicated lubricating system, a greater loss of power consumed in elevating the bearing temperature, and a shorter life of the lubricant resulting from thermal degradation taking place. On that account, numbers of measures have been proposed to suppress the rise in temperature. None of these measures is, however, free from other problems such as complicated structure, higher costs, and deteriorated bearing functions. Accordingly, there has been a need for further improvements.
FIG. 16 shows a main motor X mounted on a railcar or the like, incorporating a bearing 2 for rotatably supporting an armature shaft 1. As shown in FIG. 17, this bearing 2 is arranged with both end faces adjacent to end members 5 and 6. The end members 5 and 6 have concave grease pockets 3 and 4 for reserving grease (not shown), respectively. The bearing 2 and the end members 5 and 6 constitute a rolling bearing apparatus. In this rolling bearing apparatus, the oil component contained in the grease in the grease pockets 3 and 4 is supplied into the bearing 2 to provide long-term lubrication for the bearing 2.
The above-mentioned bearing 2 is essentially composed of an inner race 7 fitted and fastened onto the armature shaft 1 as shown in FIG. 18, an outer race 8 positioned and fixed to a not-shown housing or the like, and rolling elements 11 such as cylindrical rollers. The rolling elements 11 are interposed between rolling contact surfaces 9 and 10 formed on the raceways of the inner and outer rings 7 and 8, respectively. On both axial ends of the outer race 8 are formed ribs 12 and 13 each projecting radially inwardly from the rolling contact surface 10.
Meanwhile, the end members 5 and 6, arranged to adjoin both ends of the bearing 2, have the grease pockets 3 and 4 which are formed to communicate with open ends of the bearing 2 between the inner and outer races 7 and 8. These grease pockets 3 and 4 reserve grease whose oil component flows over the bore surfaces on the ribs 12 and 13 of the outer race 8 to the inside of the bearing 2 for lubrication.
As mentioned above, the inner race 7 of the bearing 2 is fitted and fastened onto the armature shaft 1 and therefore rotates in operation, whereas the outer race 8 is fixed to the housing or the like. Accordingly, the oil component of the grease, when supplied from the grease pockets 3 and 4 to the inside of the bearing 2, flows into the bearing 2 via the ribs 12 and 13 at the lower part of the outer race 8.
However, since the oil component of the grease to be supplied is very small in quantity and the ribs 12 and 13 of the outer race 8 constitute barriers there, the oil component ceases to flow, thereby making it difficult to provide adequate supply thereof. This difficulty in achieving satisfactory lubrication greatly lowers the durability of the bearing 2, causing a problem of shortening the life of the bearing 2.
An object of the present invention is to provide a rolling bearing with new measures to suppress a rise in temperature. To achieve the foregoing object, the present invention provides a rolling bearing which comprises a pair of races, a plurality of rolling elements interposed between the races, and a cage for retaining the rolling elements, an inner race of the pair of races being rotated in operation, the cage being guided with outer regions of its pocket surfaces in contact with the rolling elements. The present invention also provides a rolling bearing which comprises a pair of races, a plurality of rolling elements interposed between the races, and a cage for retaining the rolling elements, an outer race of the pair of races being rotated in operation, the cage being guided with inner regions of its pocket surfaces in contact with the rolling elements.
Due to the configurations that the cage in a rolling bearing whose inner race is rotated in operation is guided with outer regions of its pocket surfaces in contact with the rolling elements, and that the cage in a rolling bearing whose outer race is rotated in operation is guided with inner regions of its pocket surfaces in contact with the rolling elements, the slide resistance between the rolling elements and each cage can be reduced to suppress the generation of heat resulting from friction in the slide portions. This offers inexpensive, simple-structured measures to suppress a rise in temperature while maintaining the bearing functions.
Another object of the present invention is to facilitate satisfactory lubrication by means of the oil component exuding out of grease and to enhance the durability and life of the bearing. To achieve this object, the present invention provides a bearing apparatus which comprises a bearing, at least one end face of the bearing adjoining an end member having a concave grease pocket formed therein, the bearing including an outer race whose bore surface on its rib avoids projecting from the inner periphery of the grease pocket in the end member. Incidentally, the present invention is applicable not only in the case where the bearing has only one of its end faces adjoining the end member, but also in the case where the bearing has both end faces adjoining such end members.
Since the bore surface on the rib of the outer race is formed to avoid projecting from the inner periphery of the grease pocket in the end member, the rib of the outer race creates no barrier on the way from the grease pocket in the end member to the inside of the bearing. This facilitates adequate supply of the grease""s oil component from the grease pocket to the inside of the bearing.
Moreover, it is desirable in the present invention that the outer race be tapered over the bore surface on the rib to its rolling contact surface, or that the end member be tapered over the inner periphery of the grease pocket to the bore surface on the rib of the outer race. In such cases, the oil component of the grease can simply flow down from the grease pocket to the inside of the bearing, allowing the oil component of the grease supplied to flow into the rolling contact surface of the outer race smoothly. Incidentally, the tapering may be applied to either the bore surface of the rib on the outer race or the inner periphery of the grease pocket, or both.
Furthermore, the external surfaces of the outer race are desirably covered with an insulation film whose inner end face is flush with the bore surface on the rib of the outer race. By this means, the oil component of the grease can be readily supplied from the grease pocket into the bearing even when the present invention is applied to a bearing that has an insulation film for preventing galvanic corrosion.
The bearings stated above are applicable for those incorporated into a railcar main motor or the like to support the armature shaft rotatably.
The nature, principle, and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings in which like parts are designated by like reference numerals or characters.